1. Technical Field of the Invention
The present invention relates generally to induction bonding or joining, and more particularly to bonding or joining plastic or metallic pipe using induced energy.
2. Discussion of the Related Art
There currently exists a wide number and variety of induction heating devices. One such induction heating device is described in U.S. Pat. No. 4,521,659, issued to Buckley et al. on Jun. 4, 1985. The heating gun described therein uses a tank circuit which includes a capacitor and an inductor coil. The inductor coil is wrapped around a U-shaped pole piece which has a gap formed between the ends thereof. The capacitor of the tank circuit is connected to a power supply which provides an alternating current of predetermined frequency.
The aforementioned patent describes a technique of joining two sheets of material by placing a susceptor, such as a wire screen, between the sheets with adhesive therebetween. The heating gun is positioned above the two sheets and the screen with the ends of the pole piece touching one of the sheets and with a gap of the pole piece located above the area where the sheets are to be joined. An alternating current from the power source enters the tank circuit and the capacitor increases the Q of the tank circuit, in turn increasing the current flow through the inductor coil. Direction of the current along the inductor coil reverses at each cycle of alternating current. The current flow in the inductor coil creates a magnetic flux within the turns of the coil. The flux is picked up by the pole piece and carried to either of the two ends. The flux then jumps to the susceptor rather than across the gap to the other of the two ends. Since the sheets of material are transparent to magnetic flux, the flux is easily transferred to the screen through the sheets. The rapidly changing direction of current in the coil causes the flux to change constantly in magnitude and direction. This is also true in the metal screen as well as in the pole piece. Hysteresis creates eddy currents in the screen which result in heat being generated in the screen.
While the aforementioned heating gun is suitable for laying down a single heat zone, whereby a seam can be created between two pieces of layered material, it is sometimes desirable to join two pieces of ceramic, metallic or plastic pipe or tubing. Previously disclosed induction bonding methods do not provide a method for bonding pipe or tubing.
Previously known methods of joining pipe or tubing include open flame, forced hot air, chemical heat, and resistive heater devices. All of these techniques and devices suffer from one or more disadvantages, most significantly that of the potential for explosion when working around hazardous, inflammable fuels. Moreover, the aforementioned devices and techniques are difficult for a technician or a mechanic to handle with one hand, and are generally not capable of efficiently and effectively producing a uniform heat zone circumferentially around a cylindrical shrink fit coupling.
It is accordingly an object of the present invention to provide an apparatus for joining plastic or metallic pipes.
It is another object of the present invention to provide an apparatus for joining plastic or metallic pipes using induced energy.
It is another object of the present invention to provide an apparatus for joining plastic or metallic pipes which is more environmentally safe than previous methods.
It is yet another object of the present invention to accomplish the foregoing objects in a simple manner.
Additional objects and advantages of the present invention are apparent from the drawings and specification which follow.